Reciprocating type portable filing machine

ABSTRACT

A reciprocating type portable filing machine of a fluid actuatable structure having a finger operable valve mechanism for the pressured fluid introduction, a cylindrical reciprocator which is incorporated within a main body being resiliently loaded in axial directions, a piston slidable within the reciprocator in directions opposite to the sliding directions of the latter and a filing part coactive with the reciprocator for the filing work.

United States Patent 1191 Odawara et al.

[ Apr. 16, 1974 RECIPROCATING TYPE PORTABLE FILING MACHINE [75]Inventors: Kazuo Odawara, Funabashi;

Mituharu Magami, Chiba; Kyoichi l-lirokawa, Tokyo, all of Japan [73]Assignee: Nitto Kohki Co., Ltd., Tokyo, Japan [22] Filed: Nov. 3, 1972[21] Appl. No.: 303,430

[30] Foreign Application Priority Data July 20, 1972 Japan 47-072862[52] US. Cl. 51/170 TL [51]. Int. Cl B23d 67/00 [58] Field of Search51/170 TL, 175

[56] 1 1 References Cited UNITED STATES PATENTS 2,618,107 11/1952 Martin51/170 TL 12/1956 Larson 5l/l70 TL 10/1960 Swanson 51/170 TL PrimaryExaminer-Othell M. Simpson Assistant Examiner-Robert C. Watson Attorney,Agent, or Firm-Armstrong & Wegner [5 7] ABSTRACT A reciprocating typeportable filing machine of a fluid actuatable structure having a fingeroperable valve mechanism for the pressured fluid introduction, acylindrical reciprocator which is incorporated within a main body beingresiliently loaded in axial directions, a piston slidable within thereciprocator in directions opposite to the sliding directions of thelatter and a filing part coactive with the reciprocator for the filingwork.

12 Claims, 7 Drawing Figures 95 as 1.71.9 1 75 73 10 7780100 908366678210284101 103 7a 6074 76 92 50 4s 93 9'4 QATENTEDAPR as 191*- sum 20F 3 PATENTEDAPR 16 m4 3.803,;773 sum 3 OF 3 Fig.7 v102 RECIPROCATINGTYPE PORTABLE FILING MACHINE The present invention relates to areciprocating type portable filing machine, more particularly relates toa portable filing machine of a reciprocating type which utilizes acombined effect of fluid actuated piston movement with resilientrepulsion, the fluid being in general given in the form of compressedair.

Many proposals have been made for the improvement of the structures andfunctions of reciprocating type portable filing machines. Nevertheless,most of the conventional portable filing machines of this type are stillindispensably accompanied by undesirable drawbacks such as considerablevibrations and shocks during the filing work which are uncomfortable andirritating to the operator of the machine, and rough movement of thereciprocating, part or parts relative to the main part of the machine.For these reasons, portable filing machines of reciprocating type havenot been as welcomed in the market as portable filing machines of rotarytype.

It is the object of the present invention to provide a reciprocatingtype portable machine capable of performing surface filing withoutirritating and uncomfortable vibrations and shocks to the hands of theoperators. 7

It is also the object of the present invention to provide areciprocating type portable filing machine capable of performing surfacefiling with assured smooth movement of reciprocating part or partsrelative to the main part of the machine. In order to attain theabovedescribed objects, the portable filing machine of the presentinvention includes a hollow main body, a main hand grip disposed to thetop of the main body, a fluid actuatable reciprocator incorporatedwithin the main body and resiliently loaded in axial directions a fingeroperable valve mechanism incorporated in the main hand grip so as tocontrol the flow of the actuating fluid, a piston encased within thereciprocator, a filing part coactive with the reciprocator for thesurface filing work and a roller bearing assembly inserted between themain body and the filing partfFluid exhaust passages connected tochambers on both sides of the piston within the reciprocator maydesirably join together at a point appreciably remote from theirupstream ends so that the discharge of the used fluid should not beinfluenced by the pressure prevailing within the reciprocator.

Further featuresand advantages of the present invention will be madeclearer from the ensuing description, reference being made to anembodiment illustrated in the accompanying drawings, in which:

FIG. 1 is a vertical cross sectional plane view of an embodiment of theportable filing machine of the present invention;

FIG. 2 is a cross sectional plane view taken along a line 2-2 in FIG. I;

FIG. 3 is a cross sectional plane view taken along a line 3-3 in FIG. I;

FIG. 4 is a cross sectional plane view taken along a line 4-4 in FIG. 1;

FIG. 5 is a cross sectional plane view taken along the line 55 in FIG.1-;

FIG. 6 is a vertical cross sectional plane view of a main part of themain hand grip of the apparatus shown in FIG. 1; a

FIG. 7 is an explanatory perspective plane view of the roller bearingassembly in a disassembled condition.

Referring to FIG. 1, the entire structure of a basic embodiment of theportable filing machine of the present invention is shown. As majorelements, the machine includes a hollow main body 30; a main hand grip10, secured on the main body 30, for handling of the machine byoperators; a mechanism incorporated inside the main hand grip 10 forcontrol of flow of fluid medium used for actuation of the filing work; afluid actuated cylindrical reciprocator 60 disposed axially slidablywithin the main body 30; an axially slidable piston 80, contained withinthe cylindrical reciprocator 60, and; a filing part 90, disposeddownside of the main body 30 in rigid connection with the reciprocator60. Further, in the case of the illustrated embodiment, the main handgrip 10 is accompanied by an auxiliary front hand grip 38 threaded intothe front end part of the main body 30.

The main hand grip 10 is provided with a front bore 16 opening on thefront side at 17. The bore 16 merges into a fluid intake passage 11formed in the rear portion of the grip 10. At the front opening 17 ofthe bore 16, a trigger 19 is pivoted to the body of the grip 10 via alateral pin 20. The trigger l9 possesses a front nose 18 for operationby an operators thumb or fingers. The trigger 19 is accompanied with arearwardly extending valve actuator 21 which is pivoted to the formervia a lateral pin 22. The rear end of the valve actuator 2| confrontsthe front end of a valve member 23 incorporated within the rearwardextension of the bore 16.

The fluid intake passage 11 is connected to a given supply source of thefluid medium via a fluid intake pipe 24 which is threaded at itsdownstream end into the passage 11. This fluid intake passage 11 is connected to a vertical fluid intake passage 12. A fluid exhaust passage 13is formed in the rear portion of the grip l0, separately from the fluidintake passage 11, and is connected to a horizontal fluid exhaustpassage 15 via a vertical fluid exhaust passage 14. The fluid exhaustpassage 13 opens into a fluid exhaust pipe 25 spacedly embracing thefluid intake pipe 24. As is clear in the drawing, the fluid exhaust pipe25 is connected air tight to the rear end of the grip 10.

The main body 30 is secured to the bottom face of the main hand grip 10by set bolts 27 and 28 via an intermediate gasket 26. The main body 31is internally provided with a cylinder bore 31 which extends over theentire length of the main body and provided on the outside with anauxiliary hand grip 38 threaded at its leg portion into the frontportion of the main body.

In the main body 30, a fluid passage 34 is formed and connected with the2nd fluid exhaust passage 14 running through the body of the hand grip10. The fluid passage 34 runs horizontally, parallel to the third fluidexhaust passage 15. The fluid passage 34 terminates at a rear annulargroove 35 formed in the wall of the main bore 31. Similarly, the thirdfluid exhaust passage 15 runs further forward through the body of thehand grip l0 and isconnected to a front annular groove 37, formed in thewall of the main bore 31, via a vertical fluid passage 36 formed throughthe mainbody 30. The main body 30 is further internally provided with avertical hole 33 which joins the main bore 31 at a right angle and isconnected to the second fluid intake passage 12 in the main hand grip 10via a connecting passage 32.

The front end of the main bore 31 is closed by an end wall 41 detachablyfixed thereto by a suitable fastener ring 39. The end wall 41 isinternally and coaxially accompanied with a cushion abutment 43 securedthereto by a set bolt 45. The cushion abutment 43 is made up of elasticmaterials such as rubber or the like. A coil compression spring 47 isinserted over the cushion abutment 43 and extends between the inner faceof the end wall 41 and the front face of the fluid actuated cylindricalreciprocator 60.

On the rear end side of the main bore 31, an end wall 42, a fastenerring 40, a cushion abutment 44, a set bolt 46 and a coil compressionspring 48 are arranged in a same order as on the above-described frontend side of the main bore 31. Further, in the front and rear endregions, the main bore 31 is provided with longitudinal guide grooves 49and 50, respectively, formed in its wall.

The fluid actuated cylindrical reciprocator 60 is contained within themain bore 31 in an axially slidable arrangement. Both ends of thereciprocator 60 are closed by sealing caps 71 and 72 which are fixed inposition by pins 69 and 70, respectively. As already described, outerfaces of the caps '71 and 72 are in pressure contact with inner ends ofthe compression springs 47 and 48, respectively. The sealing caps 71 and72 are provided with downwardly protruding carrier legs 73 and 74,respectively. The carrier legs 73 and 74 serve for assemblage of thefiling part 90 to the main body 30 as later explained in more detail.

Re the fluid system, the reciprocator 60 is provided with fluid inletports 61 and fluid outlet ports 62 and 63 formed through its peripheralwall. Further, the reciprocator 60 is provided with a rear annulargroove 65 and a front annular groove 64 formed in its peripheral wall68. The wall 68 is further provided with a cut-out 66 and a passage 67connected to the cut-out 66, the cut-out 66 forming reservoir for thepressured fluid. The diameters of the fluid inlet ports 61 decrease fromthe middle one to the terminal ones 61a and 6112. In the dispositionshown in FIG. 1, the annular grooves 64 and 65 of the reciprocator 60respectively meet the annular grooves 37 and 35 of the main body 30.

The piston 80 is encased within the reciprocator 60 in an axiallyslidable arrangement leaving fluid chambers 77, 78 on both ends thereof.This piston is provided with a fluid passage 81 opening on one hand intothe leftward fluid chamber 77 and on the other hand into an annulargroove 84 formed on its periphery; and another fluid passage 82 openingon one hand into the rightward fluid chamber 78 and on the other handinto an annular groove 83 formed on its periphery also.

The filing part 90 includes a support layer 93 secured to the carrierlegs 73 and 74 of the reciprocator 60 by set bolts 75 and 76 viaintermediate members 91 and 92. A body file 95 is attached to thesupport layer 93 by holder mechanisms 97 and 98 while sandwiching acushion layer 94 of elastic nature and an intermediate friction layer 96for preventing undesirable accidental slippage of the body file 95. Theholder mechanisms 97 and 98 are located on both ends of the length ofthe filing part 90.

In between the main body 30 and the filing part 90, there is disposed aroller bearing assembly 100 which is shown in FIG. 7 in a disassembleddisposition. As is clear from the drawing, the roller bearing assembly100 includes, from top to bottom, a carrier plate 101 which carries aplurality of bearing rollers 102. The bearing rollers 102 expose theirperipheries somewhat beyond both faces of the carrier plate 101 and arearranged spacedly side by side with their axles being at right angleswith respect to the reciprocating direction of the filing part 90. Asupporter plate 103 is placed beneath the bearing rollers 102. Theabove-mentioned three members 101, 102 and 103 are received within aguide frame 104 mounted on the support layer 93. The inner length of theguide frame 104 is selected somewhat larger than the length of thecarrier plate 101 so that the latter can slide longitudinally within theguide frame 104 upon reciprocation of the filing part 90.

In practical use the portable filing machine of the present invention,having the above-explained structure functions in the following manner.

In the first place, the nose 18 of the trigger 19 is turned by thumb orfinger from the disposition shown in FIG. 1 to that shown in FIG. 6 sothat the valve member 23 is forced to slide rearwardly via the valveactuator 21. By this sliding of the valve member 23, the fluid intakepassage 11 is brought into communication with the second fluid intakepassage 12. Upon establishment of this communication, the pressuredfluid supplied from the fluid intake pipe 24 is brought into theinterior of the reciprocator passing through the fluid intake passage11, the second fluid intake passage 12, the connecting passage 32 (seeFIG. 3) and the vertical hole 33 of the main body 30. Once the trigger19 is turned in this way, the trigger 19 and the valve member 23 re tainthe disposition shown in FIG. 6 because the lateral pin 20 of thetrigger l9 assumes a position above the level of the axis of the valveactuator 21. In other words, the above-mentioned fluid flowcommunication is maintained without accidental interruption.

Now in the disposition shown in FIG. 1, both the reciprocator 60 and thepiston 80 are positioned about midway in main bore 31 interior. But, inpractical operation, they move in directions opposite each other.

Assuming that the piston 80 is positioned on a little to the right ofthat shown in the drawing, the pressured fluid is introduced into theright side fluid chamber 78 via the fluid inlet port 61 of thereciprocator 60, the annular groove 83 on the periphery of the piston 80and the fluid passage 82 within the body of the piston 80. The increasedpressure inside the fluid chamber 78 caused by this pressured fluidintroduction presses the inner face of the right side sealing cap 72and, consequently, the reciprocator 60 as a whole is moved rightwards inthe drawing, i.e. rearwards in the structure of the filing machine. Inthis case, the magnitude of the fluid pressure within the chamber 78exceeds the magnitude of the force produced by the right sidecompression spring 48. On the other hand, this fluid pressure within theright side (rear side) fluid chamber 78 forces the piston 80 to slideleftwards (forwards) in the reciprocator 60. By this leftward sliding ofthe piston 80, the right side fluid outlet ports 63 come intocommunication with the interior or reciprocator 60, i.e. the right sidefluid chamber 78, and the fluid in the chamber 78 is discharged outsidethe machine via the port 63, the annular groove of the reciprocator 60,the annular groove 35 of the main body 30, the fluid passage 34, theexhaust passages 14 and 13 and the fluid exhaust pipe 25.

By the above mentioned leftward movement of the piston 80, the annulargroove 84 of the piston 80 isregistered at the fluid inlet port 61 ofthe reciprocator 60 and the pressured fluid is now introduced into theleftward fluid chamber 77 via the inlet port 61, the annular groove 84and the fluid passage 81 of the piston 80. Due to this introduction ofthe pressured fluid into the chamber 77, the piston 80 is now urged tomove rightwards.

Separately from this, after the above-mentioned discharge of thepressured fluid out of the right side fluid chamber 78, the reciprocator60 is forced to move leftwards by the repellent force produced by theright side compression spring 48. This leftward movement of thereciprocator 60 is further assisted by the fluid pressure within thechamber 77 already caused by the leftward sliding of the piston 80 inthe reciprocator 60. The leftward movement of the reciprocator 60associated with the rightward sliding of the piston 80 within thereciprocator 60 allows communication between the leftward fluid outletport 62 and the interior of the reciprocator 60 and, due to theestablishment of this fluid flow communication, the pressured fluid isdischarged'from the left side fluid chamber 77 via the outlet port 62,the annular groove 37, the fluid passage 36, the horizontal fluidexhaust passage 15, the vertical fluid passage 14, the horizontal fluidpassage 13 and the fluid exhaust pipe 25. Shocks caused by theabove-described reciprocal movement of the reciprocator 60 in the mainbore 31 are effectively absorbed by the cushion abutments 43 and 44provided on both ends of the main bore 31 interior.

In connection with the above-described discharging system of thepressured fluid out of both side fluid chambers 77 and 78, it-should begreatly appreciated that, in the upstream part of the fluid dischargingline, pressured fluids from the different chambers flow along differentcourses and the different courses join with each other at a locationappreciably remote from the positions of the chambers. Thanks to thisspecially designed arrangement of the fluid discharging system, thedischarge of the pressured fluid can be carried out very smoothlywithout being influenced by the pressured condition inside the chambers.More specifically, in the embodiment shown in FIG. 1, the pressuredfluidlfrom the left side chamber .77 flows through the upper exhaustpassage 15, whereas the pressured fluid from the right side chamber 78flows through the lower exhaust passage 34 which runs almost parallelto, but clearly separated from, the upper exhaust passage 15. However,in the vicinity of the rear end of the interior of the main hand grip10, both passages 15 and34 merge into a common passage, i.e. theZndfluid passage 14.

The reciprocal movement of the reciprocator so caused accompaniescorresponding and concurrent reciprocal movement of the filing part 90via the carrier legs 73 and 74 of the sealing caps 71 and 72. Thisreciprocal movement of the filing part 90 is carried out very smoothlydue-to the insertion of the roller bearing assembly 100 between thebottom face of the main body 30 and the top side of the filing part 90.By the abovementioned reciprocal movement of the filing part 90,

.the body file 95 carries out the filing work'through its slidingcontact with the-surface to be finished.

So that the reciprocator 60 does not exert too much downward pressureagainst the wall-of the main bore 31 and undesirably damage the samewhen the machine is driven in an unloaded condition, the pressured fluidis introduced into the cut-out (reservoir) 66 from the annular grooves83 and/or 84 via the passage 67. By this introduction of the pressuredfluid into the underside cut-out 66, the reciprocator 60 is maintainedin a somewhat lifted condition during its reciprocation and damage tothe main bore wall can be effectively prevented.

As already described, the sealing caps 71 and 72 are fixed to the endsof the reciprocator 60 by pins 69 and 70. In a preferred embodiment ofthe filing machine of the present invention, the length of at least oneof the pins 69 and 70 is selected shorter than the inner diameter of thecylindrical reciprocator 60. By designing the pins in this way, thesealing caps 71 and 72, together with the filing part 90, can be veryeasily disassembled from the body of the machine by simply punching thepins 69 and/or 70 into the holes.

What is claimed is:

l. A reciprocating type portable filing machine comprising, incombination, a main hand grip adapted for an operators handling of themachine and provided with a fluid intake passage and a first fluidexhaust passage; a pressured fluid supply system external of said mainhand grip and connecting said fluid intake passage to a given supplysource of said pressured fluid; a used fluid exhaust system external; ofsaid main hand grip-and connected to said first fluid exhaust passage; afinger operable valve and its related assembly incorporated within saidmain hand grip for control of the pressured fluid supply through saidfluid intake passage; a hollow main body disposed to the bottom of saidmain hand grip confining a longitudinally elongated main bore which isclosed at both ends and provided with a fluid intake hole connected tosaid fluid intake passage of said main hand grip and a second fluidexhaust passage joining at its downstream end with said first fluidexhaust passage; a fluid actuated cylindrical reciprocator encasedwithin said main bore in an axially reciprocating arrangement andprovided with fluid inlet ports capable of being connected to said fluidintake hole of said main body and also provided with fluid outlet portsconnected to said first fluid exhaust passage and said second fluidexhaust passage, respectively; means arranged on both inner closed endsof said main bore and for resiliently resisting the reciprocation ofsaid reciprocator; a piston encased within said reciprocator in anaxially reciprocating arrangement and provided with fluid intakepassages communicable to said fluid inlet ports of said reciprocator; afiling part disposed downwards of said reciprocator in an arrangementcoactive with thelatter; and a roller bearing assembly inserted betweenthe bottom outer face of said main body and the upper face of saidfiling part.

actuator pivoted to said trigger and extending rearwardly through saidfront bore and a valve member disposed at the junction of said frontbore with said fluid intake passage in an arrangement capable of beingactivated by said valve actuator.

3. A reciprocating type portable filing machine as claimed in claim 1wherein cushion abutments are provided on both closed ends of said mainbore.

4. A reciprocating type portable filing machine as claimed in claim 1wherein said fluid exhaust passage joins with said first fluid exhaustpassage at a point remote from their upstream ends.

5. A reciprocating type portable filing machine as claimed in claim 1wherein the internal chamber of said reciprocator is closed at both endsby sealing caps detachably fixed to the cylindrical wall thereof.

6. A reciprocating type portable filing machine as claimed in claim 5wherein the fixing of said sealing cap to said cylindrical wall iseffected by a pin at least one of whose length is shorter than theinternal diameter of the chamber.

7. A reciprocating type portable filing machine as claimed in claim 5wherein said sealing caps are providcd with downwardly extending carrierlegs for carrying said filing part.

8. A reciprocating type filing machine as claimed in claim 1 whereinsaid fluid inlet ports of said reciprocator reduce their transversecross sectional areas as they deviate from the middle of the length ofsaid reciprocator.

9. A reciprocating type portablefiling machine as claimed in claim 1wherein said resilient resisting means is given in the form of coilcompression springs placed between outer end faces of said reciprocatorand corresponding inner closed ends of said main bore.

10. A reciprocating type portable filing machine as claimed in claim 1wherein one of said fluid intake passages of said piston opens at thefront end face of said piston and the other of said fluid intakepassages opens at the rear end face of said piston.

11. A reciprocating type portable filing machine as claimed in claim 1wherein said filing part includes a support layer, a cushion layerdisposed underneath of said support layer an intermediate friction layerdisposed underneath said cushion layer and a body file detachablyarranged underneath said intermediate friction layer.

12. A reciprocating type portable filing machine as claimed in claim 1wherein said roller bearing assembly includes a carrier plate, aplurality of bearing rollers which are axially rotatably carried by saidcarrier plate in a spaced side by side arrangement with their axesrunning at right angles to the direction of reciprocation of said filingpart, a supporter plate disposed underneath said bearing rollers and aguide frame fixed on said filing part and accommodating the aboverecited elements in its center cavity.

1. A reciprocating type portable filing machine comprising, incombination, a main hand grip adapted for an operator''s handling of themachine and provided with a fluid intake passage and a first fluidexhaust passage; a pressured fluid supply system external of said mainhand grip and connecting said fluid intake passage to a given supplysource of said pressured fluid; a used fluid exhaust system external ofsaid main hand grip and connected to said first fluid exhaust passage; afinger operable valve and its related assembly incorporated within saidmain hand grip for control of the pressured fluid supply through saidfluid intake passage; a hollow main body disposed to the bottom of saidmain hand grip confining a longitudinally elongated main bore which isclosed at both ends and provided with a fLuid intake hole connected tosaid fluid intake passage of said main hand grip and a second fluidexhaust passage joining at its downstream end with said first fluidexhaust passage; a fluid actuated cylindrical reciprocator encasedwithin said main bore in an axially reciprocating arrangement andprovided with fluid inlet ports capable of being connected to said fluidintake hole of said main body and also provided with fluid outlet portsconnected to said first fluid exhaust passage and said second fluidexhaust passage, respectively; means arranged on both inner closed endsof said main bore and for resiliently resisting the reciprocation ofsaid reciprocator; a piston encased within said reciprocator in anaxially reciprocating arrangement and provided with fluid intakepassages communicable to said fluid inlet ports of said reciprocator; afiling part disposed downwards of said reciprocator in an arrangementcoactive with the latter; and a roller bearing assembly inserted betweenthe bottom outer face of said main body and the upper face of saidfiling part.
 2. A reciprocating type portable filing machine as claimedin claim 1 wherein said main hand grip is internally provided with afront bore which opens on the front side of said hand grip and at itsrear end communicates with said fluid intake passage and said valve andits related assembly includes a finger operable trigger pivoted at thefront opening of said front bore, a valve actuator pivoted to saidtrigger and extending rearwardly through said front bore and a valvemember disposed at the junction of said front bore with said fluidintake passage in an arrangement capable of being activated by saidvalve actuator.
 3. A reciprocating type portable filing machine asclaimed in claim 1 wherein cushion abutments are provided on both closedends of said main bore.
 4. A reciprocating type portable filing machineas claimed in claim 1 wherein said fluid exhaust passage joins with saidfirst fluid exhaust passage at a point remote from their upstream ends.5. A reciprocating type portable filing machine as claimed in claim 1wherein the internal chamber of said reciprocator is closed at both endsby sealing caps detachably fixed to the cylindrical wall thereof.
 6. Areciprocating type portable filing machine as claimed in claim 5 whereinthe fixing of said sealing cap to said cylindrical wall is effected by apin at least one of whose length is shorter than the internal diameterof the chamber.
 7. A reciprocating type portable filing machine asclaimed in claim 5 wherein said sealing caps are provided withdownwardly extending carrier legs for carrying said filing part.
 8. Areciprocating type filing machine as claimed in claim 1 wherein saidfluid inlet ports of said reciprocator reduce their transverse crosssectional areas as they deviate from the middle of the length of saidreciprocator.
 9. A reciprocating type portable filing machine as claimedin claim 1 wherein said resilient resisting means is given in the formof coil compression springs placed between outer end faces of saidreciprocator and corresponding inner closed ends of said main bore. 10.A reciprocating type portable filing machine as claimed in claim 1wherein one of said fluid intake passages of said piston opens at thefront end face of said piston and the other of said fluid intakepassages opens at the rear end face of said piston.
 11. A reciprocatingtype portable filing machine as claimed in claim 1 wherein said filingpart includes a support layer, a cushion layer disposed underneath ofsaid support layer an intermediate friction layer disposed underneathsaid cushion layer and a body file detachably arranged underneath saidintermediate friction layer.
 12. A reciprocating type portable filingmachine as claimed in claim 1 wherein said roller bearing assemblyincludes a carrier plate, a plurality of bearing rollers which areaxially rotatably carried by said carrier plate in a spaced side by sidearrangement with thEir axes running at right angles to the direction ofreciprocation of said filing part, a supporter plate disposed underneathsaid bearing rollers and a guide frame fixed on said filing part andaccommodating the above recited elements in its center cavity.